1. Field of the Invention
The present invention relates to a radiation image capturing apparatus, which includes a radiation detector comprising a two-dimensional matrix of radiation detecting elements, for capturing a radiation image of a subject by applying a radiation emitted from a radiation source through the subject to the radiation detector, and a method of processing radiation image information captured by the radiation image capturing apparatus.
2. Description of the Related Art
Heretofore, there have widely been used radiation image capturing apparatus for applying a radiation to a subject and guiding the radiation that has passed through the subject to a radiation conversion panel for thereby recording radiation image information of the subject on the radiation conversion panel. The radiation conversion panel comprises, for example, a stimulable phosphor panel which is capable of storing a radiation energy representing radiation image information in a phosphor and subsequently emitting the stored radiation energy representing radiation image information as stimulated light from the phosphor by applying stimulating light to the phosphor.
In recent years, the medical field has faced demands for a system for recording radiation image information on a radiation conversion panel and thereafter immediately reading the recorded radiation image information for diagnosis or the like. To meet such demands, it has been proposed to use, instead of the stimulable phosphor panel, a semiconductor sensor employing a CCD solid-state sensor or amorphous silicon for directly converting the applied radiation into an electric signal to be read.
Efforts have been made to produce radiation conversion panels which are higher in resolution (with more pixels) and larger in area. Therefore, it is important to develop a technology for transmitting a large amount of radiation image information recorded in radiation conversion panels at a high rate to diagnostic systems or the like.
Japanese laid-open patent publication No. 2002-199388 discloses a radiation image capturing apparatus for transmitting radiation image information at a high rate through optical fibers. FIG. 13 of the accompanying drawings shows a schematic arrangement of such a radiation image capturing apparatus 2.
As shown in FIG. 13, the radiation image capturing apparatus 2 comprises an image capturing unit 4 for capturing radiation image information and a controller 6 for controlling the image capturing unit 4 and processing the radiation image information sent from the image capturing unit 4. In the image capturing unit 4, the radiation image information is recorded on a radiation conversion panel 8 which may comprise a semiconductor sensor or the like. The radiation conversion panel 8 is divided into two areas A, B which record respective items of radiation image information. When the respective items of recorded radiation image information are read from the areas A, B of the radiation conversion panel 8, they are converted into respective digital signals by A/D converters 10a, 10b. The digital signals from the A/D converters 10a, 10b are multiplexed by a multiplexer 12. The multiplexed digital signals are converted into a serial signal by a parallel-to-serial converter 14. The serial signal from the parallel-to-serial converter 14 converted by an electro-optical transducer 16 into an optical signal, which is transmitted through an optical fiber 18 to the controller 6. In the controller 6, the optical signal is converted by an optoelectrical transducer 20 into an electric signal, which is converted into a parallel signal by a serial-to-parallel converter 22. The parallel signal from the serial-to-parallel converter 22 is supplied to a CPU 24. The CPU 24 processes the parallel signal to rearrange the items of radiation image information from the areas A, B to reproduce an image from the radiation image information.
FIG. 14 of the of the accompanying drawings is a diagram showing the relationship between the serial signal supplied from the parallel-to-serial converter 14 to the electro-optical transducer 16 and the optical signal transmitted from the electro-optical transducer 16 through the optical fiber 18 to the controller 6.
As shown in FIG. 14, the serial signal comprises a series of data SAk, SAk+1, SAk+2, . . . representing the radiation image information read from the area A of the radiation conversion panel 8, and a series of data SBk, SBk+1, BAk+2, . . . representing the radiation image information read from the area B of the radiation conversion panel 8. The serial signal is supplied from the parallel-to-serial converter 14 to the electro-optical transducer 16, which converts the serial signal into an amplitude-modulated optical signal. The amplitude-modulated optical signal comprises high and low amplitude levels which represent levels “1” and “0” of the data of the serial signal.
Even though the optical fiber 18 is used to transmit the optical signal from the image capturing unit 4 to the controller 6, since the amount of data to be transmitted remains unchanged, there is a certain limitation on high-rate transmission of the signal.